Variable speed reversible drive for a harvesting apparatus

ABSTRACT

An agricultural crop harvester&#39;s feeding and gathering units are driven by a power source on the harvester through a sheave assembly journaled on a countershaft mounted towards the rear of the feeding unit. Power is then transmitted by a variable ratio V-belt drive to a speed reducing and direction reversing planetary gear unit mounted forwardly on the feeding unit and finally to the gathering and feeding mechanisms by drives of conventional design. In the variable ratio V-belt drive, the effective diameter of a split sheave output portion of the countershaft sheave assembly is selectively adjusted hydraulically while, in inverse response, the effective diameter of a spring loaded variable driven split sheave, integral with the planetary gear unit, adjusts automatically. In addition, the driven sheave is provided with a coaxial cam arrangement responsive to changes in torque transmitted so that its effective diameter also adjusts automatically to provide appropriate belt tension. Interposing a speed reducing planetary gear unit in the drive system following the V-belt drive makes possible the use of comparatively higher belt speeds and smaller sheave diameters and facilitates provision of a selectively reversible drive to the gathering and feeding units. The reversed speed of rotation of the output of the planetary unit is substantially lower than its forward speed.

BACKGROUND OF THE INVENTION

This invention relates to mechanical power transmission systems andparticularly drive systems on agricultural harvesting machines in whicha capability for varying speed and for occasional direction reversal areadvantageous, such as in the drive for a header comprising gathering andfeeding units.

It is known to mount variable speed V-belt drives on the feeding unit ofa header for driving both its gathering and feeding units. A drive ofthis general type is shown in U.S. Pat. No. 3,759,021 issued toSchreiner et al. and sharing a common assignee with the presentapplication. However, because of demands for higher performance andhigher capacity harvesting machines, individual drives are beingrequired to transmit ever higher horsepowers. Considerations ofefficiency and the need to limit overall machine size make it desirableto minimize the overall dimensions of such drives and their components.

At the same time, operators and owners of harvesting machines arerequiring designs giving more attention to safety and convenience inoperation. In difficult crop conditions it is possible to plug even thebest of machines but the increasing size and capacity of modern machinesare making it less practicable to clear blockages by hand unassisted byany power means. The need for some means of powered reversal ofgathering and feeding units has long been known and a few reversingsystems have been offered. These have tended to be bulky and relativelyexpensive single purpose units superimposed on existing drive systemsrather than integrated into them. Typically the drive reversing systemsoffered have been applied only to parts of the feeding or gatheringunits, rather than to the complete gathering and feeding system and haveenjoyed only limited commercial success. To be successful, reversersmust be reliable, simple, low cost, compact, convenient to operate andnot interfere with or detract from normal operation of the machine.

SUMMARY OF THE INVENTION

Accordingly, a principal object of this invention is to provide a drivesystem for the gathering and feeding units of a crop harvester that iscompact, efficient and economical in relation to horsepower transmittedand which provides an effective, convenient and low cost reversingfunction.

A feature of the invention is the combination of a variable ratio torqueresponsive V-belt drive with a planetary gear speed reducer in a drivesystem mounted on the side of the feeding unit and receiving its inputat a countershaft assembly from a power source on the harvester. Thespeed reducing unit is on the output side of the drive, permitting theuse of higher belt speeds and hence more power to be transmitted by thevariable ratio V-belt drive with relatively smaller sheaves and beltcross section.

A planetary gear set in itself is a most compact form of speed reducerand when it is combined in one transmission unit with a torqueresponsive sheave, as in this invention, economies in structure andbearing design are realized which result in a very compact unit. Use ofsuch a compact drive with its high specific horsepower capacity helps tominimize component weight and facilitates closer coupling of thegathering and feeding units and hence helps reduce the lift capacity andstability problems associated with the large forward mounted gatheringunits which are becoming increasingly common.

Because of wide variations in crop density and feeding rates, drives togathering and feeding units are subject to very large fluctuations inloading. By using a torque responsive sheave in the speed reducing unit,belt tension is adjusted automatically according to the torquetransmitted so that drive efficiency at all loads and belt life areimproved, and relatively smaller sheaves and V-belt cross section may beused to transmit a given horsepower. The torque responsive sheave isthus a contributory factor to the compactness of the drive.

Another feature of the invention is that the planetary gear setarrangement facilitates the provision of an optional reverse drive,conversion to which requires only the addition of a single ring gearassembly and a control linkage. This ring gear is maintained in itsradial position solely by its engagement of the planetary pinions of thegear set and no additional bearings are required. Thus provision of areversible drive does not sacrifice space and is done at low cost. Ashifting collar, splined to an output shaft, transmits output from theplanetary gear set to that shaft, selectively engaging either a sun gearfor the reduced speed forward drive or, internally, a hub plate attachedto the ring gear for the reversed drive.

It is a feature of the drive that the reverse speed of the output of thegathering and feeding units is considerably reduced over the forwardspeed so that ample torque is available for clearing blockages byreversing the direction of flow of crop material in the gathering andfeeding units and so that clearance of blockages may be effected in adeliberate and controlled fashion. The control for selecting reversedrive is placed at the operator's station so that he may clear blockagesfrom that station, safely remote from the moving parts of the machine.

Another feature of the invention is the provision of an improved sheaveand countershaft assembly including a split adjustable driving sheave inwhich hub portions of the sheave halves are mutually supporting,extending concentrically one over the other in a close fittingtelescoping relationship so that only two bearings are needed tostabilize the sheave assembly on its shaft instead of the conventionalthree, thus providing a compact assembly with respect to length of hub,reducing cost and simplifying assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side elevation of a combine embodying theinvention.

FIG. 2 is an enlarged semi-schematic partial side elevation of thecombine operator station, showing the control cable, and the feedingunit, showing the drive to the gathering and feeding units.

FIG. 3 is a further enlarged partially sectional view on line 3--3 ofFIG. 2 of the countershaft assembly showing the hydraulically adjustabledrive sheave near its maximum effective diameter setting.

FIG. 4 is a sectional view on line 4--4 of FIG. 2 of the planetarytransmission assembly showing the shifting collar engaging the planetaryoutput gear for forward drive and with the torque responsive drivensheave in its maximum effective diameter position.

FIG. 5 is a partial view, similar to FIG. 4 showing the shifting collarengaging the ring gear clutch plate for reverse drive.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The invention is embodied in a self-propelled combine having a mainseparator body indicated generally in FIG. 1 by the numeral 10, mountedon a pair of forward drive wheels 12 and steerable rear wheels 14. Anelevated operator's station 16 is mounted at the front of the separatorbody 10. A forward mounted header indicated generally by the numeral 18is pivoted on a horizontal transverse pivot (not shown) at the front ofthe separator body 10 for vertical adjustment by conventional means. Theheader includes a feeding unit indicated generally by the numeral 20 anda gathering unit indicated generally by the numeral 22. A transverselyoriented internal combustion engine 24 indicated in schematic outlineonly in FIG. 1 is mounted towards the front of the separator body 10 andhas an output power shaft 26 extending from the left-hand side of theseparator body. A belt-type drive system indicated in its entirety bythe numeral 28 is disposed on the left side of the combine and transmitspower from the engine power shaft 26 to the header 18.

The belt drive system 28 includes a primary countershaft 30 mounted onthe combine body 10 and connected to the engine power shaft 26 by aprimary countershaft belt drive indicated generally by the numeral 32. Amovable countershaft assembly 34 is mounted on the left-hand side of thefeeding unit 20 approximately coaxial with the transverse pivot of theheader 18 and is connected to the primary countershaft 30 by a headertransfer drive indicated generally by the numeral 36. A header driveshaft 38 is mounted transversely beneath the forward end of the feedingunit 20 as shown most clearly in FIG. 2. The header drive shaft 38 isconnected to the movable countershaft 30 by a header drive indicatedgenerally by the numeral 40 in FIGS. 1 and 2. Final drives to thefeeding unit 20 and the gathering unit 22 are taken from the headerdrive shaft 38 by conventional means such as the platform drive 42indicated schematically in FIG. 1.

The feeding unit 20 shown in schematic outline in FIG. 2 includes a pairof opposite upright side walls 44, a top wall 46 and a bottom wall 48.

The movable countershaft assembly 34, shown in detail in FIG. 3,includes a frame 50 for mounting it on the left-hand side wall 44 of thefeeding unit. A tubular brace 52 extends between the frame 50 and theleft-hand side wall 44 and reinforces the mounting of the countershaftassembly 34 on the feeding unit. A threaded insert 54 fixed in the endof the brace 52 and equipped with adjusting nuts 56 engages the frame 50and in conjunction with slots (not shown) in the mounting between theframe and the side wall 44 provide for adjustment of center distancebetween the countershaft assembly 34 and the header drive shaft 38. Theframe 50 embraces a sheave assembly 58 journaled on the countershaft 60which is secured in the frame by cap screws 62 and 63.

The sheave assembly 58 includes an axially fixed portion 64 and anaxially adjustable portion 66. The fixed sheave portion 64 includes aninner hub 68 journaled by bearing 70 mounted on a shouldered sleeve 72carried against the frame 50 at the inner end of the countershaft 60. Asheave 74 is concentrically mounted on the inner hub 68 and secured bycap screws 76. The sheave 74 includes a V-belt groove 78 in which ridesthe V-belt 80 of the header transfer drive 36. Integral with the sheave74 is a sheave element 82 comprising an inclined face of a conventionalV-belt groove. A cylindrical bore 84 in the fixed sheave 74 isconcentric with the countershaft 60 and surrounds an axially extendingportion of the inner hub 68 which bears a plurality of axially alignedradially extending ribs 86.

An end portion 88 of the countershaft 60 is of increased diameter, andhas an inwardly facing radial wall 90. A sleeve 92 with stepped boresclosely fitting the shaft 60 and end portion 88 and having an internalradial wall 94 is slidably disposed on the shaft so that a variablechamber 96 is formed, the opposite ends of the chamber being defined bythe radial walls 90 and 94 of the shaft and sleeve respectively. Anapproximately radial threaded hole 98 in the sleeve 92 communicates withthe chamber 96. A hydraulic hose 100 threaded into the hole 98 connectsthe chamber 96 with a source of hydraulic pressure on the combine (notshown). A single-acting hydraulic cylinder is thus constituted with theshaft 60 and its stepped end portion 88 serving as a fixed cylinder rodand piston and the sleeve 92 acting as a moving cylinder. Oil sealingbetween the sliding parts is effected by annular seals 102 and 104carried in grooves in the sleeve 92 and a bellows-type seal 106connected between the end portion 88 of the shaft 60 and the sleeve 92protects the exposed portion of the "cylinder rod". A snap ring 108carried in a groove 110 on the shaft 60 limits axial movement of thesleeve 92 in one direction. Engagement between the radial step faces 90and 94 of the shaft and sleeve respectively limits movement in theopposite direction.

The axially adjustable sheave portion 66 is journaled on the sleeve 92by a bearing 112 which abuts shoulders 114 and 116 of the sleeve 92 andsheave portion 66 respectively on opposite sides of the bearing. Ahollow generally cylindrical hub portion 118 of the sheave portion 66engages the axially fixed sheave portion 64 closely fitting andextending substantially the full length of the bore 84 for slidingmovement therein. Extending generally radially inwards from the hubportion 118 is a plurality of lugs 120 loosely engaging the ribs 86 soas to permit axial movement but prevent any substantial relativerotation between the axially fixed sheave portion 64 and the axiallyadjustable sheave portion 66. A conventional V-belt groove face 122integral with the axially adjustable sheave element 66 is concentricwith and has an inclination equal and opposite to that of thecorresponding V-belt groove face 82 on the fixed sheave portion 64, andtogether the two faces constitute the groove of a sheave of variableeffective diameter. A V-belt 124 of the header drive 40 rides in thisgroove and transmits power from the movable countershaft assembly 34 tothe header drive shaft 38 via a transmission assembly indicated in itsentirety by the numeral 126, coaxial with and drivingly engaging theheader shaft 38.

The transmission assembly 126, best shown in FIG. 4, is mounted on theleft-hand side wall 44 of the feeding unit towards its forward end by abracket assembly 128 shown only in FIG. 2 and disposed so that theheader drive shaft 38 lies transversely immediately beneath the bottomwall 48 of the feeding unit. The transmission assembly 126 combines, inan integrated unit, a planetary transmission indicated generally by thenumeral 130 and a sheave assembly indicated generally by the numeral132.

The sheave assembly 132, driven by the V-belt 124, is of the variableeffective diameter torque sensing or torque responsive type and includesan axially fixed sheave element 134 and an axially adjustable sheaveelement 136. A compression spring 138 carried between a spring retainer140 and the movable sheave element 136 biases that element axiallytowards the fixed sheave element 134 in the direction of increasingeffective diameter. The torque sensing or torque responsiveness of thesheave assembly 132 depends upon control of relative rotation betweenthe two sheave elements 134 and 136 and is effected by a cam assembly142 annularly contained between them. A torque sensing mechanism of thistype is fully described in U.S. Pat. No. 3,881,370 issued to Vogelaar etal. and sharing a common assignee with the present application and willnot be described in detail here. Suffice it to say that the cam assembly142 is so disposed between the sheave elements 134 and 136 that anytendency for relative rotation between the two sheave halves results ina cam action biasing the axially adjustable sheave element 136 towardsheave element 134. The sheave assembly 132 is rotatably carried on theheader drive shaft 38 by a hub-like extension 144 of an input sun gear146 journaled on the shaft 38 by a pair of bearings 148. The sheaveassembly 132 is drivably keyed and secured to the input gear hub 144 bya key 150 and set screws 152 respectively.

As previously mentioned, the transmission assembly 126 is mounted on theside wall 44 of the feeding unit 20 by means of the bracket assembly128. The planetary transmission 130 includes a generally annularbell-shaped gear housing 154 which includes the actual attaching points(not shown) of the transmission assembly 126 to the bracket assembly128. The inner end of the gear housing 154 includes a bearing housing156 and the outer end has an annular flange 158. A boss 160 having abore 162 parallel to the header drive shaft and communicating with theinterior of the gear housing 154 extends axially from the rearward sideof the gear housing adjacent the bearing housing 156. A pinion carrier164 closes the bell mouth of the gear housing 154 and includes a coverportion 166 secured to the flange 158 of the gear housing 154 by aplurality of fasteners 168 and, extending axially from the cover portion166, a pinion carrier structure 170. The gear housing 154 and the pinioncarrier 164 together form a gear housing assembly through which theheader drive shaft 38 rotatably extends carried by bearings 172 and 174,housed in the bearing housing 156 of the gear housing and in a centralbore of the pinion carrier 164 respectively. Annularly interposedbetween the bearings and the shaft are a shaft hub 176 and the inputgear hub 144 respectively. A woodruff key 178 drivingly connects theshaft hub 176 to the shaft. An enlarged diameter portion of the shafthub 176 extends within the gear housing 154 and includes externalsplines 180 and a snap ring groove 182 intersecting the splines.

The pinion carrier structure 170 includes a plurality of bores 184carrying a plurality of pins 188 on which are journaled, by a pluralityof bearings 190, pinion gears 192 each including as integral parts afirst planetary pinion 194 immediately adjacent the pinion carrier coverand drivably engaging the input sun gear 146 and a second planetarypinion 196 immediately adjacent the first. The second planetary pinions196 drivably engage and carry a ring gear assembly 198 which includes aring gear 200 and a concentrically dished clutch plate 202 secured tothe ring gear by a plurality of fasteners 204. The ring gear assembly isfree to float in the gear housing 154, its movement being limitedradially only by the engagement of the ring gear 200 with the secondplanetary pinions 196 and axially by the confinement of the clutch plate202 between adjacent faces 206 and 208 of the gear housing 154 andpinion carrier structure 170 respectively. An output sun gear 210 isinterposed, concentric with the header drive shaft 38, between the shafthub 176 and the input sun gear 146 and includes a spur gear portion 212drivably engaging the second planetary pinions 196 and, immediatelyadjacent the shaft hub 176, a hub-like extension 214 bearing externalsplines 216 matching those (180) of the shaft hub 176. The output sungear 210 has an internal bore 218 exceeding the diameter of adjacentportions of the header drive shaft 38 and is maintained in positionradially only by its engagement with the teeth of the second planetarypinions 196 and axially by its close confinement between the shaft hub176 and the input sun gear 146.

An internally splined shifting collar 220 is slidably carried on thematching splines of the shaft hub 176 and is axially disposable so thatthe internal splines selectively also engage (as shown in FIG. 4) ordisengage the external splines 216 of the output sun gear 210 so thatthe shaft hub 176 is selectively coupled to or uncoupled from the outputsun gear 210. An increased diameter outer portion of the shifting collar220 bears an external splined section 222 matching internal splines ofthe clutch plate 202 and the inner end of the shifting collar has anexternal annular groove 224. The shifting collar 220 is also disposableaxially so that the internal splines of the clutch plate 202 selectivelydrivably engage (as shown in FIG. 5) or disengage the matching externalsplines 222 of the shifting collar so that the shaft hub 176 isselectively coupled to or uncoupled from the ring gear assembly 198.

A shifting assembly 226 has a shaft portion 228 slidably disposed in thebore 162 of the boss 160 of the gear housing 154. The shaft 228 extendsinto the gear housing 154 and carries a shifter plate 230 which engagesthe external groove 224 of the shifting collar 220. As indicated in FIG.2, the shifter assembly 226 is connected through a linkage 232 andpush-pull control cable assembly indicated generally by the numeral 234to a control handle 236 at the combine operator's station 16.

As previously stated, the header drive shaft 38 extends transverselybeneath the feeding unit 20. Its right-hand end (not shown) extendsbeyond the right-hand side wall 44 of the feeding unit and is journaledadjacent its end in a bearing supported by the feeding unit 20. Finaldrives to the feeding and gathering units are taken from the shaft 38 byconventional means including chain or splined couplers, a typical chaincoupler half 238 being shown in FIG. 4, retained on the header driveshaft 38 by cap screw 240. A header drive arrangement, using splinedcouplers in the header drive shaft is disclosed in U.S. Pat. No. Re26,512 issued to Rohweder and sharing a common assignee with the presentapplication.

In typical harvesting operation the engine 24 is run at a constant speedand hence the sheave assembly 58 of the movable countershaft assembly 34driven by the engine through the fixed ratio primary countershaft andheader transfer belt drives 32 and 36 respectively, also rotates at aconstant speed. The gathering and feeding units are driven from thesheave assembly 58 by the V-belt 124 running in the adjustable widthV-belt groove formed by the axially fixed sheave element 64 and theaxially adjustable element 66. The combine operator selectively adjuststhe width of the groove so as to vary the linear speed of the belt 124and hence the operating speeds of the gathering and feeding unitsaccording to crop conditions. To increase operating speed, the operatormanipulates a hydraulic control (not shown) to admit oil under pressureto hydraulic cylinder chamber 96. Shaft 60 and sleeve 92 behave as asingle acting hydraulic cylinder with the rod remaining stationary whilethe body (sleeve 92) carrying the movable sheave element 66 is biasedtowards the fixed sheave element 64 in the direction of increasingeffective diameter, effectively reducing groove width and forcing thebelt 124 outwards so as to increase belt speed. When the hydraulicpressure is released, belt tension pulls the belt radially inwards so asto force the sheave sections apart expelling hydraulic oil from thechamber 96 and reducing the effective diameter of the sheave so as toreduce belt speed. It will be noted that the close fitting telescopingengagement of the hub portion 118 of the movable sheave half 66 with thebore 84 of the axially fixed sheave portion 64 is of such axial extentin relation to hub diameter that the two sheave portions are mutuallysupporting with regard to radial alignment so that two axially separatedbearings, 70 and 112, rather than the conventional three bearings, aresufficient to support the countershaft sheave assembly 58 stably on thecountershaft 60.

The transmission assembly 126 is thus driven at variable speed by theV-belt 124 engaging the groove formed between the axially fixed sheaveelement 134 and the axially movable sheave element 136. In operation,the center distance between the countershaft assembly 34 and thetransmission assembly 126 is fixed and, V-belt 124 being relativelyinelastic, changes in the effective diameter of the selectively adjusteddrive sheave of the countershaft assembly 34 must result inapproximately equal and opposite changes in the effective diameter ofthe driven sheave 132 of the transmission assembly 126. In the latter,the compression spring 138 biases the movable sheave element 136 towardsthe fixed sheave element 134 in the direction of increasing effectivediameter. However, when the chamber 96 of the hydraulic actuator ispressurized, forcing the belt 124 to run at a greater effective diameterat the countershaft, the spring 138 is overcome forcing the sheavehalves apart and allowing the belt to seek a smaller effective diameteron the driven sheave, thus increasing its speed.

Basic belt tension is set before going to the field by loosening thefasteners (not shown) securing the movable countershaft assembly 34 tothe side 44 of the feeding unit and adjusting the center distancebetween the sheaves by means of the nuts 56 on the threaded portion 54of brace 52. Under heavy load operating conditions an increase of belttension is desirable and this is achieved automatically through theaction of the torque responsive cam assembly 142. If, when the gatheringand feeding units are heavily loaded, belt 124 tends to slip, theslipping will result in relative rotational motion between the sheaveelements 134 and 136 such that cam action will bias sheave element 136towards sheave element 134 so as to increase the effective diameter ofthe driven sheave and hence increase belt tension.

Input to the planetary transmission 130 is through the input sun gear146 which is keyed to the driven sheave assembly 132, gear and sheaveassembly being journaled as a unit on header drive shaft 38. For normal(forward) harvesting operation, the operator, by means of operatinghandle 236, moves the shifting collar 220 to the position shown in FIG.4, which drivingly connects the output sun gear 210 with the headerdrive shaft 38 so that the shaft is driven through the planetary pinion192 and output gear 210 at a speed considerably slower than that of thesheave assembly 132, a preferred speed reduction ratio being between21/2 and 3:1.

To drive the gathering and feeding units in the reverse direction, forexample to clear a blockage, the operator moves the shifting collar 220to the position shown in FIG. 5 whence the ring gear assembly 198 isdrivingly connected to the header drive shaft 38. Drive is nowtransmitted from the input sun gear 146 through the planetary pinion 192and the ring gear 198 so that shaft 38 is driven in a reverse direction,a preferred gear ratio being such that reverse speed is approximatelyhalf of normal forward or harvesting speed.

If desired, the reversing capability may be made optional. If theplanetary transmission is to be used for forward, speed reducing driveonly the ring gear assembly 198 and shifting collar controls are omittedand a snap ring is fitted in groove 182 of the shaft hub 176 so as tohold the shifting collar 220 in the position shown in FIG. 4.

I claim:
 1. In a header for a mobile harvesting machine, the headerincluding gathering and feeding units and a power input shaft, theharvesting machine carrying a power source, an improved drive for theheader comprising:a drive sheave connected to and driven by the powersource; a driven sheave, coaxial with and driving the input shaft,including a first sheave half, a second sheave half coaxial with andaxially shiftable relative to the first sheave half and cooperating withit so as to define a variable effective diameter V-belt groove, at leastone of the sheave halves being rotationally deflectible relative to theinput shaft, and automatic means coaxial with the driven sheave foraxially biasing the second sheave half towards the first sheave half foradjusting the effective diameter in response to rotational deflectionbetween the driven sheave and the input shaft caused by changes in thetorque transmitted through the input shaft to the header; and a V-belttrained around the drive and driven sheaves, engaging the driven sheaveat its effective diameter, for transmitting power from the drive sheaveto the driven sheave, the automatic adjustment of the driven sheaveserving to maintain appropriate tension in the V-belt.
 2. In a mobileharvesting machine having a crop gathering unit, a crop processing unit,a feeding unit for transferring the gathered crop to the processingunit, and a power source on the harvester for driving the units, thecombination therewith of an improved drive system for the gatheringunit, carried on the feeding unit, and comprising:a drive sheave havingan adjustable effective diameter, drivingly connected to the powersource; a driven sheave; a drive belt drivingly trained around saiddrive and driven sheaves; transmission means having an input drivinglyconnected to the driven sheave and an output drivingly connected to thegathering unit and including a drive element selectively shiftablebetween a forward position and a reverse position so that, for a givendriving direction of the input, the driven direction of the output isreversed and the gathering unit is driven in forward and reversedirections respectively; first control means for shifting the driveelement of the transmission between its forward and reverse positions;and second control means for selectively changing the effective diameterof the drive sheave so as to change the speed ratio between the driveand driven sheaves and hence the driven speed of the gathering unit. 3.The invention defined in claim 2 wherein the output of the transmissionis also drivingly connected to the feeding unit.
 4. In a mobileharvesting machine having a crop gathering unit, a crop processing unit,a feeding unit for transferring the gathered crop to the processing unitand a power source, an improved drive system for driving said gatheringand feeding units comprising:a countershaft carried on the machine; arotatable input unit journaled on the countershaft, drivingly connectedto the power source and including a drive sheave having a V groove; atransmission unit mounted on the machine including a torque responsivedriven sheave having an adjustable V groove and automatic means foradjusting the effective diameter of the groove in response to changes intorque transmitted by the sheave, an output shaft drivingly connected tothe gathering and feeding unit, a speed reducing planetary gear setdrivingly connected with the driven sheave and means for drivinglyconnecting the planetary gear set with the output shaft; and a V-beltengaging the V grooves of the drive and driven sheaves and drivinglyconnecting the input unit with the transmission unit.
 5. The inventiondefined in claim 4 wherein the drive sheave has an axially fixed firstsheave half and an axially adjustable second sheave half, selectivelyadjustable so as to change the effective diameter of the drive sheaveand vary the driven speed of the gathering and feeding units.
 6. Theinvention defined in claim 5 wherein the input unit is journaled on thecountershaft by no more than two bearings and wherein the drive sheavehalves each have a hollow extended hub, each hub containing no more thanone of said bearings, one hub closely fitting and concentrically andtelescopingly engaging the other for adjustable axial movementtherebetween, the axial engagement and closeness of fit being at leastsufficient to align the sheave halves radially and concentrically in anormal working relationship with each other so that bearing supportbetween the sheave and the shaft at only two axially separated points issufficient to stablize the sheave on the countershaft.
 7. The inventiondefined in claim 4 wherein the planetary gear set and the driven sheaveare coaxial with the output shaft and the planetary gear set isimmediately adjacent and directly engages the driven sheave in thetransmission unit.
 8. The invention defined in claim 7 wherein theplanetary gear set includes at least two output elements driven inmutually opposite directions and the means for connecting the planetarygear set with the output shaft includes a clutch, selectively engageablewith the respective output elements, so that the output shaft may bedriven selectively in a forward or a reverse direction.
 9. The inventiondefined in claim 8 wherein the automatic means for adjusting theeffective diameter of the driven sheave is effective when the outputshaft is driven in both forward and reverse directions.
 10. Theinvention defined in claim 8 wherein the planetary gear set includes asun gear, at least two planet pinions engaging the sun gear, a ring geardrivingly and concentrically engaging the planet pinions and free tofloat radially, being maintained in its concentric position only throughengagement with the planet pinions, and a drive plate carried by thering gear, the sun gear and drive plate constituting two of said outputelements, and wherein the clutch is operable to selectively engage thesun gear or the drive plate for forward and reverse rotation of theoutput shaft.
 11. The invention defined in claim 10 wherein theplanetary gear set reduces the speed of rotation of the output shaft inrelation to the speed of the driven sheave in both forward and reversedirections.
 12. The invention defined in claim 11 wherein the ratio ofthe forward speed of the output shaft to the reverse speed of said shaftis between about one-to-one and two-to-one.
 13. In a drive system forthe feeding unit of a mobile harvesting machine of the type in which thefeeding unit has an inlet in a crop receiving relationship with agathering unit and an outlet in a crop discharge relationship with acrop processing unit the improvement comprising incombination:reversible drive means operatively connected to the feedingunit for selectively driving the unit in a forward direction, whereincrop material is conveyed from the inlet to the outlet, and in thereverse direction.
 14. The invention defined in claim 13 wherein thereversible drive means includes a planetary gear unit having first andsecond output elements and a shiftable control element operativelyassociated with the planetary gear unit for selectively connecting thefirst and second output elements with the feeding unit, said elementsdriving the feeding unit in forward and reverse directions respectively.15. In a mobile harvesting machine of the type in which crop material isconveyed by a feeding unit from a gathering unit to a crop processingunit, a transmission for driving the gathering unit carried by thefeeding unit and driven by a power source on the machine andcomprising:a transverse shaft drivingly connected to the gathering unit;and a planetary gear assembly including an input element connected toand driven by the power source, first and second output elements, meansdrivingly connecting the output elements to the input element forrotating the respective output elements in opposite directions, and acontrol means for selectively engaging said output elements with thetransverse shaft for forward and reverse drive of the gathering unitrespectively.
 16. The invention defined in claim 15 wherein theplanetary gear unit is coaxial with the transverse shaft.
 17. Theinvention defined in claim 15 wherein the transverse shaft extendsthrough the planetary gear unit and has opposite sections, one on eachside of the planetary gear unit, and the gathering unit includes twoportions, each portion being driven individually by an opposite sectionof the shaft.